Italian researchers compared the efficacy of oral cannabinoid treatments versus amitriptyline - an anti-depressant commonly prescribed for migraines - in 79 chronic migraine patients over a period of three months. Subjects treated daily with a 200mg dose of a combination of THC and CBD achieved a 40 percent reduction in migraine frequency - a result that was similar to the efficacy of amitriptyline therapy.

Subjects also reported that cannabinoid therapy significantly reduced acute migraine pain, but only when taken at doses above 100mg. Oral cannabinoid treatment was less effective among patients suffering from cluster headaches.

"We were able to demonstrate that cannabinoids are an alternative to established treatments in migraine prevention," researchers concluded.

Some five million Americans are estimated to experience at least one migraine attack per month, and the condition is the 19th leading cause of disability worldwide.

According to retrospective data published last year in the journal Pharmacotherapy, medical cannabis consumption is often associated with a significant decrease in migraine frequency, and may even abort migraine onset in some patients.

A just published literature review in the journal Cannabis and Cannabinoid Research concludes: "[I]t appears likely that cannabis will emerge as a potential treatment for some headache sufferers."